Aa stacked graphene-diamond hybrid material by high temperature treatment of diamond and the fabrication method thereof

ABSTRACT

There is provided a fabrication method for an AA stacked graphene-diamond hybrid material by converting, through a high temperature treatment on diamond, a diamond surface into graphene. According to the present invention, if various types of diamond are maintained at a certain temperature having a stable graphene phase (approximately greater than 1200° C.) in a hydrogen gas atmosphere, two diamond {111} lattice planes are converted into one graphene plate (2:1 conversion), whereby the diamond surface is converted into graphene in a certain thickness, thus to fabricate the AA stacked graphene-diamond hybrid material.

RELATED APPLICATION

The present disclosure relates to subject matter contained in priorityKorean Application No. 10-2008-0050480, filed on 29 May, 2008, which isherein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high functional carbon material, andmore particularly, to an AA stacked graphene-diamond hybrid material byhigh temperature treatment of diamond and a fabrication method thereof.

2. Background of the Invention

Graphene refers to one sheet of graphite, i.e., the (0001) surface ofgraphite. If graphene is stacked upon one another in a pattern of AB (orABC), it becomes generally known graphite (space group #194, p6/mmc;this is referred to as ‘AB stacked graphite’) (refer to FIG. 1). Aninterplanar spacing between graphene of the AB stacked graphite is 3.35Å.

If an element, such as Li, and the like, is intercalated into the ABstacked graphite, a stacked structure of the graphene becomes the AApattern, thus to be AA stacked graphene (space group #191, p6/mmm; thisis referred to as ‘AA stacked graphite.’) If Li is intercalated, theinterplanar spacing thereof becomes 3.706 Å, which increasesapproximately 10.6% as compared to the AB stacked graphite.

If pure AA stacked graphene without any Li intercalation is to befabricated, the interplanar spacing of graphene becomes 3.55 Å, whichhas more independent structural characteristic than the case of the ABstacked graphene. Accordingly, the AA stacked graphene may easily beseparated as well as have an excellent electrical characteristic. Inaddition, since the interplanar spacing of the AA stacked graphene isgreater than that of the AB stacked graphene by approximately 5%, it maybe used for a material exchange medium (an electrode material for a Libattery) and a Graphite Intercalation Compound (GIC) new substancedevelopment by a hetero element intercalation.

However, the AB stacked graphene is more stable than the AA stackedgraphene in terms of energy, whereby pure AA stacked graphene does notexist and even its composition is not possible.

SUMMARY OF THE INVENTION

The present invention is to epitaxially form pure AA stacked graphene ondiamond.

In addition, the present invention is to provide a method forcompounding AA stacked graphene capable of growing in units of thesecond and having an atomically flatness equivalent to a diamond surfacewhen the AA stacked graphene is to be formed on diamond.

To achieve these and other advantages and in accordance with an aspectof the present invention, there is provided an AA stackedgraphene-diamond hybrid material, including: a diamond matrix; and AAstacked graphene configured to be converted in a certain thickness from{111} lattice planes cut by a surface of the diamond matrix due to analternative loss of the {111} lattice planes.

In addition, there is provided a fabrication method for an AA stackedgraphene-diamond hybrid material, wherein a diamond matrix is maintainedwithin a temperature range having a stable graphene phase in a hydrogengas atmosphere such that a surface of the diamond matrix in a certainthickness is converted into AA stacked graphene due to an alternativeloss of {111} lattice planes cut by the surface of the diamond matrix.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic view illustrating a structure of AB stackedgraphene (generally known as graphite);

FIG. 2 is a schematic view illustrating a process of forming AA stackedgraphene from a diamond surface according to an exemplary embodiment ofthe present invention (The inset shows a structure of AA stackedgraphene);

FIG. 3 is a schematic view illustrating a structure of AA′ stackedgraphene;

FIG. 4 is an overview schematically illustrating a process offabricating an AA stacked graphene-diamond hybrid material by using asingle crystal diamond (111) substrate according to an exemplaryembodiment of the present invention;

FIG. 5 is an overview schematically illustrating a process offabricating an AA stacked graphene-diamond hybrid material by using asingle crystal diamond (110) substrate according to an exemplaryembodiment of the present invention;

FIGS. 6 a through 6 c illustrate respective processes of fabricating anAA stacked graphene-diamond hybrid material by respectively using, as amatrix, diamond powder in 6 a, a polycrystalline diamond film in 6 b,and a single crystal diamond plate in 6 c; and

FIG. 7 illustrates an XRD analysis result of a sample treated withplasma according to a first exemplary embodiment of the presentinvention, showing an epitaxial coupling between AA stacked graphenehaving an interplanar spacing of approximately 3.90 Å and a diamondsubstrate.

EFFECT OF THE INVENTION

According to the present invention, AA stacked graphene, having theinterplanar spacing of 3.5˜4.4 Å which is greater than an existing ABstacked graphite (3.35 Å) by 5˜30% and having excellent physicalproperties, may be formed on a diamond matrix with a simple process.

According to the present invention, since there is no need to have atime to generate a nucleus on the diamond matrix (i.e., incubationtime), a second unit process is enabled, and the graphene surface maymaintain flatness in an atomic level.

The diamond serves as a nonconductor (insulator), and graphene has acharacteristic of a semi-conductor or conductor. The AA stackedgraphene-diamond hybrid material may be utilized in a next generationsemi-conductor device (e.g., graphene-diamond single crystal substrate),an electrode material of a Li battery with enhanced power density (e.g.,graphene-diamond powder), and various types of a new materialdevelopment.

DETAILED DESCRIPTION OF THE INVENTION

Graphene and a diamond {111} lattice plane have a very similarstructure. Both has a hexagonal ring structure of carbon atoms [Here,the former has a flat hexagonal ring shape while the latter has abuckled hexagonal ring shape], and lattice constant error is only 2%(For spacing between neighboring atoms, diamond is 1.45 Å and grapheneis 1.42 Å).

Accordingly, as an exemplary method for fabricating graphene, a methodfor “growing” graphene on the diamond {111} lattice plane has beenconsidered. Detailed descriptions regarding such method have alreadybeen given by this research team in Korean Patent Application No.2007-0081989.

The present invention has proposed another method for fabricatinggraphene, in which diamond is treated under a condition that thegraphene phase is stable so as to “convert” {111} lattice plane cut bythe diamond surface into graphene. Here, the “cut {111} lattice plane”signifies that the {111} lattice plane existing inside a diamond crystalis cut by the diamond surface, and thusly is different from the diamondsurface.

For the conversion, an interplanar spacing of the diamond {111} latticeis 2.06 Å, and an interplanar spacing of the stacked AA graphene(hereinafter, also referred to as ‘AA stacked graphene’) isapproximately 3.55 Å which is the double. Thus, two diamond {111}lattice planes become (are converted into) one graphene. That is, thediamond lattice plane and graphene perform a 2:1 conversion (refer toFIG. 2). Here, atomic hydrogen is coupled onto the diamond {111} latticecut by the graphene/diamond interface. Due to the structuralcharacteristic of the diamond {111} lattice plane, if a graphene plateis formed on the diamond {111} lattice plane through 2:1 conversion, theAA stacked graphene is formed. It should be noted that if a grapheneplate is formed through 1:1 conversion, AA′ stacked graphene may beformed (refer to FIG. 3). However, AB stacked graphite is not presented.

The diamond {111} lattice plane within a single diamond crystal consistsof 4 planes: (111), (−111), (1−11) and (11−1). (Here, the symbol “−”indicates a minus symbol in the Miller index.) On all diamond surfaces,one or more {111} lattice planes being cut are exposed. Graphene isformed through 2:1 conversion on an extension of the {111} lattice planecut by the diamond surface, and is formed perpendicularly to any one ofthe lattice plane of the 4 {111} lattice planes (refer to FIGS. 2, 4,and 5). Since the diamond formed by covalent bond is a directionalcrystal, a formation angle of graphene varies according to the surfaceconstituting the diamond surface. That is, if the diamond surface is the(111) plane, an angle (formation angle) between the diamond surface andthe graphene plate is 90° (refer to FIGS. 1 and 4), and for the (110)plane, a formation angle is 60° (refer to FIG. 5), and for the (100)plane, a formation angle is 30° (not shown).

The concept of 2:1 conversion by a high temperature treatment in thepresent invention is that the diamond {111} lattice plane cut by thesurface is etched to be disappeared. Therefore, the “conversion” of thediamond, differently from the “growth” of the graphene, does not need tohave a latent period (˜several tens of minutes) of a nucleus formationrequired for “growth,” thus to enable a short time process in units ofthe second, similar to a general etching process. In addition, since thediamond surface is converted, the surface of the formed AA stackedgraphene may maintain a flatness which is equivalent to an initialdiamond surface (flat atomically).

Hereinafter, description of the preferred embodiment of the presentinvention will be given in more detail.

The fabrication method for an AA stacked graphene-diamond hybridmaterial according to the present invention consists of (1) preparingdiamond serving as a matrix, and (2) performing a high temperaturetreatment on the diamond so as to convert a layer having a thickness ofseveral Å˜several μm on a diamond surface into AA stacked graphene.

Preparation of Diamond Matrix

Both a single crystal diamond and a polycrystalline diamond may be usedas a matrix, and formed in the shape of powder, a film, a plate or thelike. For instance, diamond powder having a size of several nm˜1 mm, asingle crystal diamond plate having a size of several mm, or apolycrystalline CVD diamond film having a size of approximately severaltens cm may be used. Preferably, the diamond powder may be used toobtain a powdered graphene/diamond hybrid material, the single crystaldiamond plate for an electron device application, and a polycrystallineCVD diamond film for other substrate material application. If the CVDdiamond film is to be used, it is more preferable to use a diamond thatis deposited on a silicon wafer in the form of a thin film (thickness˜μm) in terms of an economy.

High Temperature Treatment

The high temperature treatment on the diamond serving as the matrix isperformed in the range of a temperature (in general, approximately1,200˜1,800° C.) having a stable graphene phase within a vacuumcontainer capable of maintaining a hydrogen gas atmosphere. The hightemperature treatment may be performed using heat, plasma or a laser. Ifa laser is used to perform the high temperature treatment, there is anadvantage that graphene may be locally (e.g., a dot, a line shape)formed on the diamond matrix.

A minimum value of the temperature range having the stable graphenephase may slightly vary according to chemical vapor conditions (e.g., apresence or absence of plasma formation, gas pressure, or the like). Thehigh temperature treatment using heat is performed at an area where asurface temperature of the matrix is in the range of approximately1,300˜1,800° C., and the high temperature treatment using a plasmadevice may be performed at an area where a surface temperature of thematrix is lowered to approximately 1,200˜1,600° C. If a temperature islower than the minimum value of the temperature range, a conversion fromdiamond into graphene may be difficult. If a temperature is greater thanthe maximum value thereof, the entire sample may be converted into theAB stacked graphite. In addition, if the high temperature treatmentusing a laser is to be performed, a surface temperature of the matrix isroom temperature (below several hundreds ° C.), and temperature of anarea contacting a laser beam may be greater than 2,000° C. depending onlaser power.

After performing such high temperature treatment, as shown in FIG. 2,the diamond {111} lattice planes cut by the surface before performingthe high temperature treatment are alternatively lost due to hightemperature treatment, thereby being converted into AA stacked graphene(refer to the inset in FIG. 2). Such conversion is progressed from thesurface of the diamond matrix toward the inside thereof. Due to acrystal structure of the diamond, an interplanar spacing of the grapheneon the graphene/diamond interface is 4.38 Å. As a length of the graphenelayer becomes longer, this interplanar spacing is gradually contractedto 3.55 Å considered as an ideal interplanar spacing of the AA stack.

Hereinafter, description of the exemplary embodiment of the presentinvention will be given. However, this description is intended to beillustrative, and not to limit the scope of the claims. It should alsobe understood that the above-described embodiments but rather should beconstrued broadly within its scope as defined in the appended claims.

Example 1

AA stacked graphene-diamond hybrid powder was prepared by using diamondpowder (size: 1˜2 μm) as a matrix (refer to FIG. 6 a).

A device used for the high temperature treatment was a multi-cathodedirect current power plasma diamond synthesizer. After diamond powderwas placed on to a molybdenum substrate, the diamond/substrate set wasplaced on an anode of the synthesizer for plasma treatment. Theconditions of the plasma treatment are as follows: 200 sccm of hydrogengas, a pressure of 100 Torr, and a molybdenum substrate at a temperatureof approximately 1200° C. (Surface temperature of the diamond matrix isexpected to be higher than that of the substrate by several tens ° C.).A processing time was 1 minute.

According to the result of analyzing this sample by X-Ray Diffraction(XRD), as shown in FIG. 7, a (001) peak (2θ=22.9°) of the AA stackedgraphene, together with a diamond (111) peak (2θ=43.8°) and a (110) peak(2θ=75.4°) was observed. This indicated epitaxial coupling between theAA stacked graphene having an interplanar spacing of approximately 3.90Å and the diamond substrate. According to the result of analyzing thissample by High-Resolution Transmission Electron Microscopy (HRTEM), thethickness of the AA graphene layer was several tens nm, which verifiesthe 2:1 conversion relationship between the diamond {111} lattice planeand the graphene. Therefore, the AA stacked graphene-diamond hybridpowder could be obtained.

Example 2

A diamond/silicon plate in which diamond having a thickness of 5 μm wasdeposited on a silicon substrate having a diameter of 4″ and a thicknessof 0.5 mm was used as a matrix (refer to FIG. 6 b), and was undergonethe plasma treatment for 10 seconds under the same condition as Example1.

According to the result of analyzing the sample treated with the plasmaby HRTEM, it could be observed that the thickness of the AA graphenelayer was several nm, and the 2:1 conversion relationship between thediamond {111} lattice plane and graphene. Accordingly, the AA stackedgraphene-diamond hybrid layer could be obtained on the siliconsubstrate.

Example 3

A polycrystalline CVD diamond film having a ground (abraded, polished)<110> texture (10×10×0.5 mm³T) was used as a matrix, and was undergonethe plasma treatment for 10 minutes under the same condition as Example1 (here, the substrate temperature was 1250° C.).

According to the result of analyzing the treated sample by HRTEM, it wasobserved that the thickness of the AA graphene layer was severalhundreds nm, and the 2:1 conversion relationship between the diamond{111} lattice plane and graphene. According to the result of analyzingthis sample by rocking curve XRD, it was observed that graphene wasoriented having an angle of 60° with respect to the diamond surface(i.e., (110) plane). This is identical to the schematic diagram as shownin FIG. 5. Accordingly, it could also be checked that the formationangle of AA stacked graphene was changed on the diamond as the surfaceconstituting the diamond surface is changed.

Meanwhile, due to the structural characteristic of the diamond crystal,if the diamond surface consists of the (100) plane, the formation angleof graphene is 30°.

Example 4

A 5×5×1 mm³T single crystal (110) diamond plate was used as a matrix(refer to FIG. 6 c), and was undergone the plasma treatment for 30seconds under the same condition as Example 1 (here, the substratetemperature was 1300° C.).

According to the result of analyzing the plasma-treated sample by HRTEM,it was observed that the epitaxial coupling between the AA stackedgraphene of approximately 1 nm and the diamond surface. Although thetemperature in this Example was higher than that in Examples 1 and 2,the length of the graphene layer was shown to be shorter than those inExamples 1 and 2. This may be analyzed that the single crystal had adifficulty of being converted into graphene since the single crystal hasfew crystal defect.

Example 5

A polycrystalline CVD diamond film having a ground <110> texture(10×10×0.5 mm³T) was used as a matrix, and was undergone the heattreatment for 10 minutes in a hydrogen atmosphere in a vacuum furnace(vacuum furnace without a plasma) at a temperature of approximately1400° C.

According to the result of analyzing the heat-treated sample by HRTEM,it was observed that the thickness of the AA graphene layer was severalnm, and the 2:1 conversion relationship between the diamond {111}lattice plane and graphene. Therefore, the AA stacked graphene-diamondhybrid film was obtained.

Example 6

A polycrystalline CVD diamond film having a ground <110> texture(10×10×0.5 mm³T) was used as a matrix, and was undergone the lasertreatment in a hydrogen atmosphere in a vacuum furnace having a laserdevice therein. The scan rate of a laser beam was maintained at 1mm/min.

According to the result of analyzing a track (trace) of the laser beamby HRTEM, the AA graphene layer was observed.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present disclosure. The presentteachings can be readily applied to other types of apparatuses. Thisdescription is intended to be illustrative, and not to limit the scopeof the claims. Many alternatives, modifications, and variations will beapparent to those skilled in the art. The features, structures, methods,and other characteristics of the exemplary embodiments described hereinmay be combined in various ways to obtain additional and/or alternativeexemplary embodiments.

As the present invention may be embodied in several forms withoutdeparting from the characteristics thereof, it should also be understoodthat the above-described embodiments are not limited by any of thedetails of the foregoing description, unless otherwise specified, butrather should be construed broadly within its scope as defined in theappended claims, and therefore all changes and modifications that fallwithin the metes and bounds of the claims, or equivalents of such metesand bounds are therefore intended to be embraced by the appended claims.

1. An AA stacked graphene-diamond hybrid material, comprising: a diamondmatrix; and AA stacked graphene configured to be converted in a certainthickness from a {111} lattice plane cut by a surface of the diamondmatrix due to an alternative loss of the {111} lattice planes.
 2. The AAstacked graphene-diamond hybrid material of claim 1, wherein a hydrogenatom is coupled onto the cut diamond {111} lattice on which the grapheneand diamond are not coupled, on an interface (hereinafter, referred toas ‘graphene/diamond interface’) between the AA stacked graphene and theconverted diamond matrix.
 3. The AA stacked graphene-diamond hybridmaterial of claim 1, wherein an interplanar spacing on the AA stackedgraphene surface is smaller than that on the graphene/diamond interface.4. The AA stacked graphene-diamond hybrid material of claim 1, whereinthe diamond matrix is formed in the shape of powder, a film or a plate.5. The AA stacked graphene-diamond hybrid material of claim 1, whereinthe diamond matrix is a single crystal or polycrystalline diamond.
 6. Afabrication method for an AA stacked graphene-diamond hybrid material,wherein a diamond matrix is maintained within a temperature range havinga stable graphene phase in a hydrogen gas atmosphere such that a surfaceof the diamond matrix in a certain thickness is converted into AAstacked graphene due to an alternative loss of {111} lattice planes cutby the surface of the diamond matrix.
 7. The fabrication method of claim6, wherein the conversion is progressed from the surface of the diamondmatrix to an inside thereof.
 8. The fabrication method of claim 6,wherein heat, plasma or a laser is used such that the diamond matrix ismaintained within a temperature range in which a graphene phase isstable.
 9. The fabrication method of claim 8, wherein for the heattreatment, a surface temperature of the diamond matrix is 1,300˜1,800°C.
 10. The fabrication method of claim 8, wherein for the plasmatreatment, a surface temperature of the diamond matrix is 1,200˜1,600°C.
 11. The fabrication method of claim 8, wherein for the lasertreatment, a surface temperature of the diamond matrix is roomtemperature, and a temperature of an area contacting a laser beam isgreater than 2,000° C. depending on laser power.